If we are leaking radio messages into space, the inhabitants of other
planets, if they exist, might be doing the same thing. Large radio
telescopes on Earth could detect such radio leaks from civilizations in
nearby star systems, as well as stronger signals dispatched from planets
thousands of light years away.

This realization is the keystone of SETI  the Search for
Extraterrestrial Intelligence. SETI is an effort to locate evidence of
past or present communicative civilizations in the universe,
particularly within our own galaxy. (The Drake
Equation provides one way to make a rough estimate of how many such
civilizations exist.)

The idea of searching for extraterrestrial life has been dreamed of
through the ages, but the spark behind contemporary methodology began in
1959 when two physicists from Cornell asserted that microwave radio
waves could be used for interstellar communication. One year later,
young astronomer Frank Drake (who later became president of the SETI
Institute) began his own microwave radio search throughout the galaxy.
Drake pointed an 85-foot antenna towards two Sun-like stars and analyzed
the reception for two months. The antenna didn't pick up any unique
frequencies, but the project inspired a new generation of SETI
scientists.

A decade later, NASA established a SETI program. It continued until the
early 1990s, when SETI funding was cut after being ridiculed on the floor of Congress
as a search for "little green men." Since then, the SETI Institute, a
non-profit corporation, has taken over the search, as have several other
privately-funded SETI projects. (No public money is being spent on SETI
today.)

More on SETI Want more on this topic? Dive deeper into the Web with our list of SETI links.